Conventional electronic coupling electrodes have produced undesired side effects in nerve blocking and nerve stimulating applications. The undesired side effects may include, for example, tissue damage. The damage may occur, for example, due to the fact that conventional electrodes carry current via electrons while nerve tissues carry current via ions. (See, for example, Krames, Elliot S., Neuromodulation, Academic Press, 072009. 152.) Delivery of DC through standard platinum electrodes has produced signs of tissue damage within 20 seconds and therefore is not a practical solution for chronic human use.
Undesired or pathological hyperactivity in the peripheral nervous system occurs in many disorders and diseases. This undesired or pathologic hyperactivity may result in undesired motor or sensory effects. Additionally, some medical conditions resulting in chronic pain (e.g., neuromas) are characterized by undesired afferent activity in peripheral nerves. Treatment may include blocking the conduction of these pathological or undesirable signals to mitigate the effects of these conditions. However, conventional conduction blocks may have employed conventional electrodes that lead to undesired side effects.
Uncoordinated or unwanted generation of nerve impulses is a major disabling factor in many medical conditions. For example, uncoordinated motor signals produce spasticity in stroke, cerebral palsy and multiple sclerosis, resulting in the inability to make functional movements. Involuntary motor signals in conditions such as tics and choreas produce incapacitating movements. Undesirable sensory signals can result in peripherally generated pain. Over-activity in the autonomic nervous system can produce conditions such as hyperhydrosis. If these nerve impulses can be interrupted along the peripheral nerves in which they travel, these disabling conditions can be managed or eliminated.
Conventional nerve blocks that prevent the propagation of an action potential through a nerve have been achieved using high frequency alternating current (HFAC), using single phase current (e.g., direct current), and through combinations thereof. HFAC, where the frequency ranges between, for example, 2 kHZ and 50 kHZ, can completely yet reversibly block the motor fibers in a peripheral nerve. In a conventional nerve blocking apparatus, HFAC is typically delivered through one or more conventional electrodes, which has provided sub-optimal results due, at least in part, to the design of the conventional electrodes.
Conventional nerve blocking has also been achieved by applying a prolonged single phase current to a nerve. The single phase current can be, for example, a direct current (DC). Conventional attempts to apply prolonged DC to a nerve have also lead to tissue damage.
A conduction nerve block that does not generate an onset response has been achieved through a combination of direct current and HFAC. Once again, conventional attempts to apply either HFAC and/or prolonged DC to a nerve have produced tissue damage.